(a) Field of the Invention
This invention relates to a process for the preparation of an aminoaryl thiophosphate or aminoaryl phosphate by hydrolysis of the corresponding N-acetylaminoaryl thiophosphate or N-acetylaminoaryl phosphate.
(b) Description of the Prior Art
Aminoaryl thiophosphates and aminoaryl phosphates are compounds that are important as intermediates for the manufacture of isocyanates dyestuffs, and the like.
In the prior art, one common process for the preparation of an aminoaryl thiophosphate or phosphate comprises forming a nitroaryl thiophosphate or phosphate by nitration of a triaryl thiophosphate or phosphate or by reaction of nitrophenol sodium with phosphorus thiochloride or phosphorus oxychloride, and then reducing the nitro groups to amino groups. However, this process involves a safety problem because of the explosive properties of nitroaryl thiophosphates or phosphates, p-nitrophenol sodium, and the like, and has the disadvantage of requiring a complicated procedure and great expenses. These reasons make the above process unsatisfactory for industrial purposes.
Alternatively, it is conceivable that an aminoaryl thiophosphate or phosphate is obtained by hydrolysis of an N-acetylaminoaryl thiophosphate or phosphate. One prior art process for the hydrolysis of such acetylamino groups comprises heating a starting material in an aqueous alkaline solution. However, when this process is applied to N-acetylaminoaryl thiophosphates or phosphates having phosphoric ester linkages, not only the acetylamino groups but also the phosphoric ester linkages undergo hydrolysis. As a result, the desired product is obtained only in low yield.